AS3955 datasheet(43/111 Pages) AMSCO

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ams Datasheet

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[v1-01] 2015-Apr-29

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AS3955 − Detailed Description

The basic assumption of Tunneling mode is that MCU is

responsible for generating the response and that AS3955 takes

care of the response synchronization over RF. For this reason,

AS3955 has a possibility to transmit ACK and NACK by issuing

a direct command (see section Direct Commands). The MCU can

also transmit data by writing the data into the buffer and issuing

a Transmit command. The implementation of Tunneling mode

also requires the handling of the SLP_REQ command since all

the received data in SELECTED state are stored in the buffer and

will not be processed by AS3955. This also implies that MCU has

to take care of correct transition of the tag into SLEEP or SENSE

state by using one of the three available commands Go To Sleep,

Go To Sense and Go To Sense / Sleep.

Data Transaction in Tunneling Mode

Figure 47 shows an example of how communication in

Tunneling mode should be implemented.

Figure 47:

Read First, then Acknowledge

ACK and NACK responses can be replaced by data, in case of an

incoming READ command.

Relevant Registers, Interrupts and Commands

Registers:

• Buffer Status Register 1 and Buffer Status Register 2 (data

length and error type)

PCD

AS3955

DATA

ACK / N

ACK

MCU

DATA

RD O

CMD A

CK / NA

DATA

Rx start

Rx end, crc or parity error,

buffer error

Tx end

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